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May 30, 2017

The Myth of Eight Glasses a Day

by John Hastings

Eight glasses of water a day. That’s what you read in magazines, that’s what your mother tells you, that’s what your friends swear by. But hang on: Is that eight measuring cups? Is it the amount in eight tumblers? And why eight, anyway?

In reality, the amount of fluid you need to stay hydrated depends on your diet, your activity levels and your body’s demands, says Debra Epstein, RD, assistant director of nutrition at Northwell’s Long Island Jewish Forest Hills Hospital. “Eight cups a day is really just a starting point -- it may not be enough if you’re working out or spending a lot of time outdoors,” she says. Falling short can leave you with a headache or muscle cramps, and can even raise your risk of heat exhaustion or potentially deadly heat stroke. Stay hydrated and safe this summer by following these simple rules:

Don’t wait until you’re thirsty. Once your tongue feels parched, you’re already mildly dehydrated, says Ms. Epstein. Keep a water bottle by your side and sip regularly to keep up with your body’s needs. You can track how well you’re doing by taking a peek at your urine. Light yellow or clear? Your body’s well-hydrated and happy. Intensely yellow or dark? You need to drink up.

Have a pre-exercise drink or two. Start your summer walks and workouts well-hydrated by downing a couple of glasses of water an hour before you exercise. Then, a half-hour before you head out, down another eight ounces. “Being fully hydrated gives you a reserve when you really start to sweat, which can come in handy with the humid conditions in our area,” Ms. Epstein says.

Let your diet help you hydrate. You don’t always have to lift a glass to top off your water supply -- if your diet is a healthy one with generous amounts of fruits and vegetables, you can eat a good portion of the water you need. “Produce contains a lot of water, and it comes packed with nutrients,” says Ms. Epstein. Watermelon, cucumber, strawberries and tomatoes are all good choices at more than 90% water, but any produce you enjoy will help you get the fluid you need.

Water alone isn’t always enough. If you’re going to be active for less than 60 minutes at a stretch, plain water will do the job, says Ms. Epstein -- but if you head out for a high-intensity hike or bike ride that will last longer than an hour, you might want a sports drink that will replace the sodium you’re losing in sweat and the carbohydrates you’re burning for fuel. As for after your workout, consider downing a glass of milk. You may not associate it with hard-core athletics, but it’s high in the potassium, carbs and protein you need.